Getting path aliases from tsconfig to work

[Nikola-Milovic]

Hello everyone, I made a small reproducible monorepo to showcase the issue I am facing. I am using tsup to bundle my internal packages. I have an UI package that is shared, and I use path aliases for this package, but when I do so it fails everytime with [ERROR] Could not resolve "@company/frontend-shared/utils/random"

This is the repo and a small readme

I had a lot of issues with this monorepo, this is my 5th or 6th iteration and it seems to be working correctly. Using relative paths works, but using the path aliases inherited from the base tsconfig doesn't work

The project is using PNPM workspaces

EDIT:

I managed to hack together a solution in terms of a plugin

import { defineConfig } from "tsup";
import { PluginBuild } from "esbuild";
import path from "path";

const aliasPlugin = (input: Record<string, string>) => {
  const aliases = Object.keys(input);
  const re = new RegExp(`^(${aliases.map((x) => escapeRegExp(x)).join("|")})`);

  return {
    name: "alias",
    setup(build: PluginBuild) {
      build.onResolve({ filter: re }, (args) => {
        const path = args.path;
        let resolvedPath = "";
        for (const alias of aliases) {
          const regex = new RegExp(escapeRegExp(alias));
          if (regex.test(path)) {
            const matchedAlias = path.match(regex);
            const restPath =
              path.substring(0, matchedAlias.index) + path.substring(matchedAlias[0].length);

            resolvedPath = input[alias] + "/" + restPath + ".ts";
          }
        }
        return { path: resolvedPath };
      });
    },
  };
};

export default defineConfig({
  esbuildPlugins: [
    aliasPlugin({
      "@company/frontend-shared/": path.resolve(__dirname, `./src/`),
    }),
  ],
});

function escapeRegExp(string: String) {
  return string.replace(/[.*+?^${}()|[\]\\]/g, "\\$&");
}

It doesn't work with -dts flag,

@company/frontend-shared:build: DTS Build start
@company/frontend-shared:build: src/components/Loader.tsx(1,27): error TS2307: Cannot find module '@company/frontend-shared/utils/random' or its corresponding type declarations.

And there is issue with file names, I have to hardcode the filetype as such fullPath = input[alias] + "/" + rest + ".ts";, otherwise it cannot find the file

Any improvements are welcomed but this seems more esbuild related than tsup